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Thread: Bonding screw in the distribution (sub) Panel

  1. #21
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    Quote Originally Posted by HI9869 View Post
    So what does a 3 phase have? 3 hots, neutral, and ground? Thank you for clarifying.
    Exactly. Five wire.
    Another Al in Minnesota

  2. #22
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    3 PHASE, 4 OR 5 WIRE FEEDERS

    Many industrial 3 phase feeders do not utilize a neutrial (grounded conductor), and are therefore 4 wire (conductor) circuits.If their are no phase to neutrial loads, the neutrial does not need to extend past the service disconnect,

  3. #23
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    Quote Originally Posted by HI9869 View Post
    So from my prospective as a home inspector I am usually inspecting homes that are 10-20 years old and I see and point out that grounds and neutrals should be separated in the sub panel. How important (as a safety issue) should this be corrected. Had a building inspector tell me it is not required to correct unless they are adding/upgrading the sub panel.
    A couple things. First here Name:  ground bar.jpg
Views: 162
Size:  19.2 KB is a typical panel ground bar. Another post explained to you about insulated bars that have a green screw through them. As you can see this bar is bare so by its nature it will be in contact with the can. By code grounding wires, (the green or bare wires) have to be connected to all non current carrying metal parts of electrical components (within reason).

    Second, the issue you cite here. What I have found is that many old houses were built with a meter outside and then the feeder extended well inside the house to the first means of disconnect usually a panel with the neutrals and the grounds bonded at that point. Later some person installs a disconnect outside but no one is astute enough to know that they have to replace the feeder and separate them. In this area I have seen less reputable (IMO) electrical contractors quote cheap sight unseen knowing that it is typical in this area, and then offer a huge upcharge to fix the problem once they start the work.


    I know what I don't know, and I know where to go to find it!

  4. #24
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    Quote Originally Posted by LRB View Post
    Many industrial 3 phase feeders do not utilize a neutrial (grounded conductor), and are therefore 4 wire (conductor) circuits.If their are no phase to neutrial loads, the neutrial does not need to extend past the service disconnect,
    Yes, but this thread is about a home inspector's questions about common dwellings, just saying. . . and the means of bonding the panel enclosure to the equipment grounding conductor via terminal bars.
    Another Al in Minnesota

  5. #25
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    Quote Originally Posted by LRB View Post
    Many industrial 3 phase feeders do not utilize a neutrial (grounded conductor), and are therefore 4 wire (conductor) circuits.If their are no phase to neutrial loads, the neutrial does not need to extend past the service disconnect,
    OP is a HI and probably almost never sees 3 phase installations.

    But we can throw in even more confusion with 3 phase 3 wire applications

  6. #26
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    three phase question

    Al and Kwired, you are absolutly correct, however the OP opened this can of worms in thread 19, asking about three phase systems, therefore I was responding to the OP question in thread 19.

  7. #27
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    Quote Originally Posted by Strathead View Post
    What I have found is that many old houses were built with a meter outside and then the feeder extended well inside the house to the first means of disconnect usually a panel with the neutrals and the grounds bonded at that point. Later some person installs a disconnect outside but no one is astute enough to know that they have to replace the feeder and separate them. In this area I have seen less reputable (IMO) electrical contractors quote cheap sight unseen knowing that it is typical in this area, and then offer a huge upcharge to fix the problem once they start the work.
    Strathead, this, in my opinion, is part of the core of what the home inspector is trying to understand, so, please pardon my nitpicking terms here.

    The wiring between the electric meter and the "first means of disconnect," the Service Disconnect, is not a "feeder", but, rather, is still the service conductors, as there is no separate neutral conductor and equipment grounding conductor, but there is only a "grounded service conductor".

    A "feeder" is the wiring between the Service Equipment and the final overcurrent protective device (most commonly fuse or circuit breaker). The Service Equipment houses the Service Disconnecting Means, the Main Bonding Jumper (that bonds the feeder neutral and equipment bonding conductor together to the Grounded Service Conductor) and it houses circuit breakers or fuses.

    A feeder neutral carries current normally, and, in order to not leak current, is an insulated conductive path all the way back to the Service Equipment.

    The subpanel metal enclosure does not "normally" carry any current. However it is connected (bonded) to the Equipment Grounding Conductor in order to create an effective fault clearing conductive path in the event of a live conductor shorting to the metal enclosure.

    This is the answer to the heart of the OP home inspector's question, in my opinion.
    Another Al in Minnesota

  8. #28
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    Quote Originally Posted by al hildenbrand View Post
    Strathead, this, in my opinion, is part of the core of what the home inspector is trying to understand, so, please pardon my nitpicking terms here.

    The wiring between the electric meter and the "first means of disconnect," the Service Disconnect, is not a "feeder", but, rather, is still the service conductors, as there is no separate neutral conductor and equipment grounding conductor, but there is only a "grounded service conductor".

    A "feeder" is the wiring between the Service Equipment and the final overcurrent protective device (most commonly fuse or circuit breaker). The Service Equipment houses the Service Disconnecting Means, the Main Bonding Jumper (that bonds the feeder neutral and equipment bonding conductor together to the Grounded Service Conductor) and it houses circuit breakers or fuses.

    A feeder neutral carries current normally, and, in order to not leak current, is an insulated conductive path all the way back to the Service Equipment.

    The subpanel metal enclosure does not "normally" carry any current. However it is connected (bonded) to the Equipment Grounding Conductor in order to create an effective fault clearing conductive path in the event of a live conductor shorting to the metal enclosure.

    This is the answer to the heart of the OP home inspector's question, in my opinion.
    I have no problem with you clarifying. Terms are important to the code. So if you are going to correct me isn't it actually "service entrance conductors"?

    Seriously though, I feel this is partly at the core of what the HI needs to know anyway, so if he is reading this and it doesn't makes sense please ask for clarification.


    I know what I don't know, and I know where to go to find it!

  9. #29
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    Quote Originally Posted by Strathead View Post
    . . . isn't it actually "service entrance conductors"?
    An interesting point. I deliberately chose "Service Conductors" as the Article 100 Definition I wanted to use because it side steps the Overhead / Underground parts of those other two definitions for Service-Entrance Conductors.

    Service Conductors. The conductors from the service point to the service disconnecting means.
    Concise and to the point in this discussion, in my opinion.
    Another Al in Minnesota

  10. #30
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    Quote Originally Posted by HI9869 View Post
    I am a home inspector trying to understand what is correct and why in the distribution (sub) panel. My understanding is that beyond the service disconnect point (main panel) (in what I call the sub panel, I believe is called a distribution panel by NEC) ground (bare copper wire) and neutral (white wire) is separated and not bonded. My question is then is the ground bus bar bonded to the panel it self with the green screw? I have asked building inspector locally and electricians locally and I can not seem to get a clear understanding. So, hopefully someone can lay this out in laymen terms so I can be a better inspector. Thank you in advance.
    Pretty Simple.
    Simply Float the Neutral Terminal Bar (No contact with panel enclosure) in your sub-panel AND install a grounding terminal bar directly to the sub-panel enclosure which will now bond the enclosure. There is nothing wrong with installing the green screw into the ground bar, but it's not necessary if the bar ground bar is already screwed to the sub-panel frame.

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